From f5626961762063b382f5fd680ff3f0851f5eac93 Mon Sep 17 00:00:00 2001
From: Sean DuBois <sean@siobud.com>
Date: Mon, 8 Jul 2024 14:28:09 -0400
Subject: [PATCH] Add APPEND_CANDIDATE

Performs SDP munging so users can insert arbitrary candidates
---
 README.md                 |  4 +++-
 internal/webrtc/webrtc.go | 14 ++++++++++++--
 internal/webrtc/whep.go   |  2 +-
 internal/webrtc/whip.go   |  2 +-
 4 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/README.md b/README.md
index 7ae90a1..482e214 100644
--- a/README.md
+++ b/README.md
@@ -203,7 +203,7 @@ The backend can be configured with the following environment variables.
 - `SSL_CERT` - Path to SSL certificate if using Broadcast Box's HTTP Server
 - `SSL_KEY` - Path to SSL key if using Broadcast Box's HTTP Server
 
-- `NAT_1_TO_1_IP` - Announce IPs that don't belong to local machine (like Public IP). delineated by ','
+- `NAT_1_TO_1_IP` - Announce IPs that don't belong to local machine (like Public IP). delineated by '|'
 - `INCLUDE_PUBLIC_IP_IN_NAT_1_TO_1_IP` - Like `NAT_1_TO_1_IP` but autoconfigured
 - `INTERFACE_FILTER` - Only use a certain interface for UDP traffic
 - `NAT_ICE_CANDIDATE_TYPE` - By default setting a NAT_1_TO_1_IP overrides. Set this to `srflx` to instead append IPs
@@ -216,6 +216,8 @@ The backend can be configured with the following environment variables.
 - `TCP_MUX_ADDRESS` - If you wish to make WebRTC traffic available via TCP.
 - `TCP_MUX_FORCE` - If you wish to make WebRTC traffic only available via TCP.
 
+- `APPEND_CANDIDATE` - Append candidates to Offer that ICE Agent did not generate. Worse version of `NAT_1_TO_1_IP`
+
 ## Network Test on Start
 
 When running in Docker Broadcast Box runs a network tests on startup. This tests that WebRTC traffic can be established
diff --git a/internal/webrtc/webrtc.go b/internal/webrtc/webrtc.go
index a6f0e87..9a409a9 100644
--- a/internal/webrtc/webrtc.go
+++ b/internal/webrtc/webrtc.go
@@ -190,14 +190,15 @@ func createSettingEngine(isWHIP bool, udpMuxCache map[int]*ice.MultiUDPMuxDefaul
 		udpMuxOpts []ice.UDPMuxFromPortOption
 		err        error
 	)
-	networkTypes := []webrtc.NetworkType{webrtc.NetworkTypeUDP4, webrtc.NetworkTypeUDP6}
+	networkTypes := []webrtc.NetworkType{webrtc.NetworkTypeUDP4}
+	udpMuxOpts = append(udpMuxOpts, ice.UDPMuxFromPortWithNetworks(ice.NetworkTypeUDP4))
 
 	if os.Getenv("INCLUDE_PUBLIC_IP_IN_NAT_1_TO_1_IP") != "" {
 		NAT1To1IPs = append(NAT1To1IPs, getPublicIP())
 	}
 
 	if os.Getenv("NAT_1_TO_1_IP") != "" {
-		NAT1To1IPs = append(NAT1To1IPs, strings.Split(os.Getenv("NAT_1_TO_1_IP"), ",")...)
+		NAT1To1IPs = append(NAT1To1IPs, strings.Split(os.Getenv("NAT_1_TO_1_IP"), "|")...)
 	}
 
 	natICECandidateType := webrtc.ICECandidateTypeHost
@@ -348,6 +349,15 @@ func newPeerConnection(api *webrtc.API) (*webrtc.PeerConnection, error) {
 	return api.NewPeerConnection(cfg)
 }
 
+func appendOffer(in string) string {
+	if extraCandidate := os.Getenv("APPEND_CANDIDATE"); extraCandidate != "" {
+		index := strings.Index(in, "a=end-of-candidates")
+		in = in[:index] + extraCandidate + in[index:]
+	}
+
+	return in
+}
+
 func Configure() {
 	streamMap = map[string]*stream{}
 
diff --git a/internal/webrtc/whep.go b/internal/webrtc/whep.go
index cdfbc40..dfac82e 100644
--- a/internal/webrtc/whep.go
+++ b/internal/webrtc/whep.go
@@ -151,7 +151,7 @@ func WHEP(offer, streamKey string) (string, string, error) {
 		timestamp:  50000,
 	}
 	stream.whepSessions[whepSessionId].currentLayer.Store("")
-	return peerConnection.LocalDescription().SDP, whepSessionId, nil
+	return appendOffer(peerConnection.LocalDescription().SDP), whepSessionId, nil
 }
 
 func (w *whepSession) sendVideoPacket(rtpPkt *rtp.Packet, layer string, timeDiff int64, sequenceDiff int, codec videoTrackCodec) {
diff --git a/internal/webrtc/whip.go b/internal/webrtc/whip.go
index d3c3bea..eea58a0 100644
--- a/internal/webrtc/whip.go
+++ b/internal/webrtc/whip.go
@@ -185,5 +185,5 @@ func WHIP(offer, streamKey string) (string, error) {
 	}
 
 	<-gatherComplete
-	return peerConnection.LocalDescription().SDP, nil
+	return appendOffer(peerConnection.LocalDescription().SDP), nil
 }